Heel attachment by screwnail



March 25, 1969 G. LlscHER ET AL 3,434,171

HEEL ATTACHMENT BY SCREWNAIL Original File d Sept. 21. 1964 Sheet of 4 March 25, 1969 a. LISCHER ET L 3,434,171

HEEL ATTACHMENT BY SCREWNAIL I Original Filed Sept. 21, 1964 Sheet 2 of 4 Fig 2 March 25, 1959 USCHER ET AL 3,434,171

HEEL ATTACHMENT BY SCREWNAIL Original Filed Sept. 21. 1964 Sheet 3 M 4 Fig. 2

March 25, 1969 L sc ET AL 3,434,171

HEEL ATTACHMENT BY SCREWNAIL Original Filed Sept. 21, 1964 Sheet 4 of 4 United States Patent US. Cl. 12-147 2 Claims ABSTRACT OF THE DISCLOSURE In a heel attaching process for securely anchoring a loose plastic heel to a lasted shoe having an insole by means of a single screwnail actuated by a striking device, the steps of compressing the lasted shoe and heel together; aligning a screwnail having a double thread with the axis of the bore of the last but spaced from the insole; and then actuating the striking device to drive the screwnail through the bore of the last through the lasted insole and into the heel for the purpose of preliminarily and finally anchoring the screwnail to prevent detachment thereof by mechanical means, thereby eliminating the necessity of preliminary boring the preliminary perforation of the insole and heel, and the necessity of rem-oval of the last from the shoe during the attaching process.

This application is a division of our copending application Ser. No. 397,711, filed Sept. 21, 1964, and now abandoned.

This invention relates to the process for attaining, in one operative step, a durable attachment of the heel to a lasted shoe, by means of a fastening element such as a screwnail, utilizing only one such fastening element, without necessitating any previous auxiliary attachment, and without necessitating removal of the last from the shoe, and also without necessitating boring or puncturing a perforation for the screwnail beforehand in the heel.

Previously, for fastening heels to insoles it was customary to utilize either a plurality of nails, for example, five or seven, which were driven into the preattached heel, or several cross-sloted screws having a wood cutting thread and having a conical portion at the head within a cross-slot screw driver connection was provided. It was discovered that these cross-slotted screws are suitable for a preliminary fastening, but not for a durable final attachment of the heel, since they were not solid enough. Furthermore, the insertion of the screw driver required too much time, and this is not necessary any more according to our novel process.

The invention resides in providing a self-cutting cylindrical screw stern, having a double thread and a truncated-cone tip, with a flat head of relatively small diameter which is driven by one single stroke through the bore in the last, the insole into the leather or plastic heel, without bursting or rupturing the heel; but which is, at the same time, sufficiently firmly attached, particularly at the head. This screwnail attachment can be employed without varying the lasts during the assembly-line-type shoe manufacturing process, since the striking tools can become effective through the bore of the last without unlasting the shoe, and since only a single fastening element need be hammered in. Thereby, two operating steps, namely, the unlasting and the relasting, are saved; a good shape of the shoe is ensured; and the rotation of the lasts is lessened.

For this purpose, a specially equipped heel attachmg machine is provided as shown in my copendmg U.S.

patent application Ser. No. 397,711, wherein a screwnail is inserted in a driver sleeve before the lasted shoe to be assembled is placed thereon, which lasted shoe can be instantaneously connected with the heel while being firmly presed together with the latter. By the sudden penetration into the plastic material of the heel by the screwnail, this material is locally rapidly heated and plastically deformed so that the scored parts of the shank of the screwnail will be firmly anchored therein.

Another important point also is the discovery obtained by nailing tests that the fiat head of the screwnail must not protrude over or above the insole, and that its side facing the shank must be a substantially fiat slightly conical shape in order to be able to afiix the substantially thinner insole durably to the heel.

It is also essential according to our method to do away with any preliminary heel boring or attaching operations, all of which require time and expense, but must be able to drive the shank of our novel fastening element through a thin layer of insole material into a much stronger heel material, in a self-cutting manner. For this purpose, a coarse cutting thread is provided.

According to our invention the screwnail is inserted, standing upright within the driver sleeve through the bore of the last which is aligned with the driver sleeve when the last is placed in the shoe, and hence the screwnail is confined during its movement within fixedly determined boundaries conforming with the dimensions of the head of the screwnail and the diameter of the driver sleeve. The underside of the head of the screwnail must offer a sufliciently large annular area to the material of the insole as is necessary for the durability of the attachment. However, the length of the shank of the screwnail is somewhat limited by the undulated, wavy, or bent shapes of the heels themselves.

In the drawings, the machine tools and the screwnail are illustrated with reference to one embodiment.

FIGURE 1 is a side elevation, partly in section, through a heel attaching machine on which the process is based.

FIGURE 2 shows the hydraulic upper clamping device for the heel, in a vertical section.

FIGURE 3 is a vertical section through the hydraulic mechanism for driving the screwnails and the last support in connection therewith.

FIGURES 4-5 represent an elevational view and a top view of a normal cross-slotted screw, and

FIGURES 6-7 illustrate, in comparison with the lastmentioned figures, a novel screwnail of the type to be employed in connection with the present invention.

FIGURE 8 shows the position of the driven-in screwnail in the heel of a shoe.

The machine for attaching the heel by means of a screwnail has been described in detail in our above-mentioned patent application. It will suffice to note here that the last for the shoe upper (FIG. 8) has a bore having a last sleeve 188 seated therein. By means of this sleeve 188, the last is placed inverted upon the screw driver sleeve 56 (FIG. 3) into whose upper end there was previously inserted a screwnail according to FIGS. 6 and 7.

The heel is appropriately positioned on the insole 179, (FIG. 8), and is fixed by the holding device 38, FIGS. 1 and 2. Thereupon, the hydraulically actuated last pusher 54 approaches the crest of the last of the shoe from below. Heel holder 38 and last compressor 54 tightly compress the parts to be assembled against each other, under pressure increase. At the suitable moment, i.e., when the pressure in the cylinder 52, FIG. 3, has become so large that it overcomes the force of the spring 64, the piston 62 drives the screwnail through the insole into the heel as shown in FIG. 8.

A preferred screwnail which has been found particularly adapted for securing the heel is illustrated in FIGS. 6

and 7, as compared with a conventional cross-slot screw 176 (FIGS. 4 and 5) such as has hitherto been used for securing heels. Screw 176 has, due to the prominent conical projection 177 on the underside of the screw head 178, only a narrow annular face 178 on the underside thereof, the width b of which is just sufiicient for presecuring a heel but is not suflicient for a permanent attachment. Even if the screws are turned very firmly through the insole 179 into the heel, the narrow annular face 178 is not of adequate width to resist the stresses set up during the wearing of the boot or shoe, and the heel will therefore often tear olf after a short time. The almost completely flat head 181 of our novel screwnail (FIG. 6) however has an annular face 182 of width B the area of which is about double that of the annular surface b. In addition to the normal screw thread 184, this screwnail is also formed with a steep helical self-cutting thread 186 which under the force exerted by the driving means 62 of the heel-attaching machine (FIG. 3) penetrates of its own accord, with its plain pointed leading tip 183, through the insole 179 into the heel and, due to its large annular head surface B, retains the said heel so firmly on the insole 179 that tearing-out of the screwnail is not to be feared. In this connection, it is an essential factor that the head of the screwnail, despite its large annular face, can be kept so small in diameter that it can be freely introduced through the sleeve 188 of the last (FIG. 8) and through the driver sleeve 56 (FIG. 3) introduced therein. One or more ribs 182 (FIG. 6) may be provided on the underside of the screwnail head, in order to additionally sustain the screwnail against turn- Due to our novel mode of heel attachment, the advantages of screwing-on of the heel for rigid seating, and of nailing-on the heel for rapid operation and easy penetration, are combined, whereas the disadvantages of low slip resistance of the nail, and relatively slow screwing action of the screw with an excessively small annular face, are avoided. Additionally, due to the approximate doubling of the annular surface B, a degree of rigidity is achieved which is necessary for a safe attachment of the heel utilizing only one single screw and the presecuring of the heel simultaneously constitutes the final attachment of the heel so that only one operating step is necessary for attaching the heel.

We claim:

1. In a heel attaching process for securely anchoring a loose synthetic plastic heel to a lasted shoe having an insole by means of a single screwnail including a single elongated shank portion having a double thread thereon actuated by a striking device, the steps of providing a last having a single bore of constant diameter extending entirely therethrough and terminating opposite the heel portion of the last; compressing the lasted shoe and heel together; inserting said single screwnail having a double thread within said single bore of the last but spaced from the insole with said screwnail being aligned with the axis of said bore, said screwnail having an enlarged head with a wide flat annular surface on its underside; and then axially actuating the striking device thereby driving the screwnail by impact through said single bore of the last, through the lasted insole and into the heel to preliminarily and finally anchor the screwnail to prevent detachment thereof by mechanical means, thereby eliminating the necessity of preliminary boring and preliminary perforation of the insole and heel, and the necessity of removal of the last from the shoe during the attaching process.

2. In a process according to claim 1, said screwnail being provided with a fine thread along its cylindrical shank extending spirally in the longitudinal direction, and being provided with steep spiral grooves along the shank extending at a greater pitch than the fine threads, said grooves being cutting edges; said screwnail having a plain truncated conical outer tip.

References Cited UNITED STATES PATENTS 1,055,174 3/1913 Holler 151-37 2,324,479 7/1943 Brandt 12-125 2,332,710 10/1943 Goodchild 12-l47 2,393,990 2/1946 Kamborian 1Zl47 2,423,908 7/1947 Small 12147 3,238,546 3/1966 Dziki et a1. 12-125 3,348,251 10/1967 Appleton et a1. 12147 CARL W. TOMLIN, Primary Examiner.

RAMON S. BRITTS, Assistant Examiner.

US. Cl. X.R. -47; 15137 

